Resist reflow measurement key and method of forming a fine pattern of a semiconductor device using the same

ABSTRACT

In a resist reflow measurement key, and method of fabricating a fine pattern of a semiconductor device using the same, the resist reflow measurement key includes a first reflow key including a plurality of first pattern elements each having a first pattern with a first radius of curvature located on a first side of a first center line and a second pattern with a second radius of curvature located on a second side of the first center line, and a second reflow key including a plurality of second pattern elements each having a third pattern with a third radius of curvature located on a first side of a second center line and a fourth pattern with a fourth radius of curvature located on a second side of the second center line, the second reflow key being formed on a same plane of a substrate as the first reflow key.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a measurement key used in semiconductordevice fabrication and a method of fabricating a semiconductor deviceusing the same. More particularly, the present invention relates to aresist reflow measurement key used for measuring the flow of resist anda method of forming a fine pattern of a semiconductor device using thesame.

2. Description of the Related Art

Due to widespread demand for semiconductor devices having an increasedprocessing speed and highly integrated memory devices for use in a widerange of electronic devices, there is a need to develop a circuitryproduct having a sub-micron size. To satisfy this need in highlyintegrated devices, efforts to develop an improved photoresistcomposition have been accelerated. Moreover, efforts to obtain a patternhaving more precise dimensions to obtain, in particular, a patternsuitable for a structure having a minimum feature size have beenaccelerated. To fabricate highly integrated semiconductor devicessuccessfully, it is necessary to form more precisely and finely aphotoresist pattern widely used in etch and ion implantation processes.To realize these products, a sensitive photoresist is required. However,use of a sensitive photoresist is necessarily accompanied by anadditional process, which is complicated.

In a semiconductor fabrication process using a single layer resist and a0.13 μm process, ArF lithography technology is used. It is forecast,however, that greater precision and dimension control will be requiredfor a process below 0.10 μm, which will be used in the future.

The wavelength of a light source for exposure directly influences theminimum resolution that can be obtained in an exposure apparatus. Forinstance, in forming a fine line and space (L/S) pattern, a g-lineexposure apparatus has a resolution limit of about 0.5 μm and an i-lineexposure apparatus has a resolution limit of about 0.3 μm. The recenttrend, however, shows that the device design rule is approaching an USmeasurement value below about 0.2 μm. It is forecast that the allowableminimum feature size in a next generation device design rule willcontinue to decrease. In particular, in fabricating a highly integrateddevice that requires a small contact hole having a high aspect ratio inan US pattern having a fine critical dimension (CD), or a cell arrayregion of a device, various processes to overcome the resolution limitof exposure apparatuses have been developed. A reflow process using heatis one example of such a process.

In a reflow process using heat, an initial photoresist pattern havingformed therein a contact hole, which has a size larger than the CD of afinal L/S pattern or the size of a contact hole to be formed, is firstformed. Then, the formed photoresist pattern is heated to a temperatureabove the glass transition temperature (Tg) of the photoresist and isreflowed to form a fine pattern. The heating reduces the viscosity ofthe linked photoresist to reflow the photoresist. Thus, the CD of the USpattern or the size of the contact hole is reduced, thereby obtaining adesired fine pattern.

In the reflow process, the CD of the reflowed resist pattern ismonitored at the after flow inspection (AFI) stage. The exposure dose iscontrolled on the basis of the CD value measured in the AFI stage. Inthe process of controlling the CD of the resist pattern in theaforementioned manner, the amount of time required to monitor the CD ofthe reflowed resist pattern in the AFI stage is very important becauseit influences the throughput of the whole exposure process.

Until recently, monitoring the CD of the reflowed resist patterninvolved measuring the CD of the reflowed resist pattern using ascanning electron microscope (SEM) in the AFI stage. In other words, inapplying the present reflow process using heat, the resist pattern,which is reflowed in the AFI stage, is monitored by an SEM and anexposure dose is controlled on the basis of the monitored result. Thus,it takes a significant amount of time to perform a process that cansatisfy a desired CD size since the monitoring in the post-developmentbaking (PDB) step, i.e., in the reflow step of the resist, depends onlyon the CD measurement using the SEM. As a result, performing the CDmonitoring on the entire region of a wafer takes too long, therebysignificantly reducing throughput as a size of the wafer increases.

SUMMARY OF THE INVENTION

The present invention is therefore directed to a resist reflowmeasurement key and a method of forming a fine pattern of asemiconductor device using the same, which substantially overcome one ormore of the problems due to the limitations and disadvantages of therelated art.

It is a feature of an embodiment of the present invention to provide aresist reflow measurement key that enables the flow of a reflowed resistpattern to be quantitatively monitored within a very short time informing a fine pattern to overcome the resolution limit of an exposureapparatus by a reflow process using heat.

It is another feature of an embodiment of the present invention toprovide a method of forming a fine pattern to overcome the resolutionlimit of an exposure apparatus by a process set to quantitativelymonitor the flow of a reflowed resist pattern within a very short timein forming a fine pattern of a semiconductor device by a reflow processusing heat.

It is still another feature of an embodiment of the present invention toprovide a resist reflow measurement key and a method of forming a finepattern of a semiconductor device using the same that is able to monitorthe flow of the resist pattern on the wafer in an AFI step within a veryshort time to improve throughput when the process is performed on wafershaving a relatively large size.

It is yet another feature of an embodiment of the present invention toprovide a resist reflow measurement key and a method of forming a finepattern of a semiconductor device using the same that is able to obtainfeedback rapidly in the reflow process of the resist pattern, decreaseAFI monitoring turn around time (TAT), and enhance pattern uniformityaccording to the position on the wafer.

At least one of the above and other features and advantages of thepresent invention may be realized by providing a resist reflowmeasurement key including a first reflow key disposed on a substratearound a first center point, the first reflow key including a pluralityof first pattern elements each having a first pattern with a firstradius of curvature located on a first side of a first center lineextending in a lengthwise direction of each of the plurality of firstpattern elements and a second pattern with a second radius of curvaturelocated on a second side of the first center line, which is opposite tothe first side of the first center line, and a second reflow keydisposed on the substrate around a second center point, the secondreflow key including a plurality of second pattern elements each havinga third pattern with a third radius of curvature located on a first sideof a second center line extending in a lengthwise direction of each ofthe plurality of second pattern elements and a fourth pattern with afourth radius of curvature located on a second side of the second centerline, which is opposite to the first side of the second center line, thesecond reflow key being formed on a same plane as the first reflow key.

The first reflow key may have a rectangular shape and the plurality offirst pattern elements may be four first pattern elements, each one ofthe four first pattern elements constituting a side of the rectangularshaped first reflow key.

The second reflow key may have a rectangular shape and the plurality ofsecond pattern elements may be four second pattern elements, each one ofthe four second pattern elements constituting a side of the rectangularshaped second reflow key.

The first pattern of each of the plurality of first pattern elements maybe a plurality of first pattern shape portions positioned at the firstside of the first center line and having the first radius of curvature,and the second pattern of each of the plurality of first patternelements may be a plurality of second pattern shape portions positionedat the second side of the first center line and having the second radiusof curvature, which is larger than the first radius of curvature, andthe third pattern of the plurality of second pattern elements may be aplurality of third pattern shape portions positioned at the first sideof the second center line and having the third radius of curvature, andthe fourth pattern of the plurality of second pattern elements may be aplurality of fourth pattern shape portions positioned at the second sideof the second center line and having the fourth radius of curvature,which is larger than the third radius of curvature.

The plurality of first pattern elements may be respectively arrangedsuch that the plurality of second pattern shape portions is disposedfacing a first direction of a line extending diagonally through thefirst center point, and the plurality of second pattern elements may berespectively arranged such that the plurality of fourth pattern shapeportions is disposed facing a second direction, which is opposite to thefirst direction, of a line extending diagonally through the secondcenter point.

The first and second reflow keys may be respectively arranged such thatat least one of the plurality of first pattern shape portions of theplurality of first pattern elements faces a corresponding one of theplurality of third pattern shape portions of the plurality of secondpattern elements.

The first reflow key and the second reflow key may be respectivelyarranged such that at least one of the plurality of second pattern shapeportions of the plurality of first pattern elements faces acorresponding one of the plurality of fourth pattern shape portions ofthe plurality of second pattern elements.

The first reflow key and the second reflow key may be respectivelyarranged such that at least one of the plurality of first pattern shapeportions of the plurality of first pattern elements faces acorresponding one of the plurality of third pattern shape portions ofthe plurality of second pattern elements and at least one of theplurality of second pattern shape portions of the plurality of firstpattern elements faces a corresponding one of the plurality of fourthpattern shape portions of the plurality of second pattern elementsconcurrently.

The first radius of curvature and the third radius of curvature may bethe same. The second radius of curvature and the fourth radius ofcurvature may be the same.

The second reflow key may have a size smaller than a size of the firstreflow key. The second reflow key may be formed in a region defined bythe first reflow key.

The first and second reflow keys may each be of a trench type pattern.The first and second reflow keys may each be of a mesa type pattern.

The first reflow key and the second reflow key are formed of a materialselected from positive photoresist and negative photoresist.

At least one of the above and other features and advantages of thepresent invention may be realized by providing a method of forming afine pattern of a semiconductor device including forming a resistpattern on a semiconductor substrate to form a pattern having apredetermined shape, forming a resist reflow measurement key on thesemiconductor substrate while forming the resist pattern, reflowing theresist pattern and the resist reflow measurement key at the same time,measuring a variation in a position of a first center point of thereflowed resist reflow measurement key and a variation in a position ofa second center point of the reflowed resist reflow measurement key byusing an optical overlay measurement apparatus, and determining acritical dimension of the reflowed resist pattern from measurementvalues of the variation in the position of the first center point andthe variation in the position of the second center point.

The pattern having the predetermined shape may be a contact hole patternor a line and space pattern.

The optical overlay measurement apparatus may be a laser scan alignment(LSA) type overlay measurement apparatus or a field image alignment(FIA) type overlay measurement apparatus.

The resist pattern and the resist reflow measurement key may be formedof an identical material.

The semiconductor substrate may include a device region where an actualdevice is formed and a test element group (TEG) region where a testdevice for measuring an electrical property of the actual device isformed, the resist pattern being formed in the device region, and theresist reflow measurement key being formed in the TEG region.

According to an embodiment of the present invention, after the reflowprocess of the resist pattern formed on the device region of the waferis performed, a variation in a position of a center point due to theflow in the resist reflow measurement key reflowed concurrently with theresist pattern is measured in the AFI step using an overlay measurementapparatus to monitor the CD of the resist pattern. Accordingly, the flowof the resist pattern on the wafer in AFI step can be monitored within avery short time, thereby improving throughput when the process isperformed on wafers having a relatively large sized. Also, in the reflowprocess of the resist pattern, feedback can be rapidly obtained, AFImonitoring turn around time (TAT) can be shortened, and patternuniformity according to the position on the wafer can be enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent to those of ordinary skill in the art bydescribing in detail exemplary embodiments thereof with reference to theattached drawings in which:

FIG. 1 illustrates a plan view of a resist reflow measurement keyaccording to an embodiment of the present invention;

FIG. 2 shows a series of SEM photographs observed through afterdevelopment inspection (ADI) before flowing a photoresist material andSEM photographs observed through after flow inspection (AFI) afterflowing the photoresist material;

FIG. 3 illustrates a sectional view of a resist reflow measurement keyaccording to an embodiment of the present invention and taken along lineII-II′ of FIG. 1;

FIG. 4 illustrates a sectional view of a resist reflow measurement keyaccording to another embodiment of the present invention and taken alongline II-II of FIG. 1; and

FIG. 5 is a flow chart of a method for forming a fine pattern of asemiconductor device according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Korean Patent Application No. 2003-67434, filed on Sep. 29, 2003, in theKorean Intellectual Property Office, and entitled: “Resist ReflowMeasurement Key and Method of Forming a Fine Pattern of a SemiconductorDevice Using the Same,” is incorporated by reference herein in itsentirety.

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof the invention are shown. The invention may, however, be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. In thefigures, the dimensions of layers and regions are exaggerated forclarity of illustration. It will also be understood that when a layer isreferred to as being “on” another layer or substrate, it can be directlyon the other layer or substrate, or intervening layers may also bepresent. Like reference numerals refer to like elements throughout.

FIG. 1 illustrates a plan view of a resist reflow measurement key 50according to an embodiment of the present invention.

Referring to FIG. 1, a resist reflow measurement key 50 according to anembodiment of the present invention includes a first reflow key 100including a plurality of first pattern elements 110, 120, 130, 140 and asecond reflow key 200 including a plurality of second pattern elements210, 220, 230, 240.

The plurality of first pattern elements 110, 120, 130, and 140constituting the first reflow key are arranged around on a first centerpoint C, on a semiconductor substrate. The plurality of first patternelements 110, 120, 130, and 140 have pattern shapes having differentradii of curvature at opposite sides of a first center line 100 cextending in a lengthwise direction of each of the plurality of firstpattern elements 110, 120, 130, and 140. In other words, each of theplurality of first pattern elements 110, 120, 130, and 140 includes afirst pattern shape portion 102 positioned at a first side of andextending in the lengthwise direction of the first center line 100 c.The first pattern shape portion 102 has a first curvature radius. Eachof the plurality of first pattern elements 110, 120, 130, and 140further includes a second pattern shape portion 104 positioned at asecond side of the first center line 100 c, which is opposite to thefirst side. The second pattern shape portion 104 has a second radius ofcurvature, which is larger than the first radius of curvature. In FIG.1, the second pattern shape portion 104 is shaped as a substantiallystraight line and thus has an infinite radius of curvature.

The plurality of second pattern elements 210, 220, 230, and 240constituting the second reflow key 200 are arranged on a same plane asthe plurality of first pattern elements 110, 120, 130, and 140 and arearranged around a second center point C₂ on the semiconductor substrate.The plurality of second pattern elements 210, 220, 230, and 240 havepattern shapes having different radii of curvature at opposite sides ofa second center line 200 c extending in a lengthwise direction of eachof the plurality of second pattern elements 210, 220, 230, and 240. Inother words, each of the plurality of second pattern elements 210, 220,230, and 240 includes a third pattern shape portion 202 positioned at afirst side of and extending in the lengthwise direction of the secondcenter line 200 c. The third pattern shape portion 202 has a thirdradius of curvature. Each of the plurality of second pattern elements210, 220, 230, and 240 further includes a fourth pattern shape portion204 positioned at a second side of the second center line 200 c, whichis opposite to the first side. The fourth pattern shape portion 204 hasa fourth radius of curvature, which is larger than the third radius ofcurvature. In FIG. 1, the fourth pattern shape portion 204 is shaped asa substantially straight line and thus has an infinite radius ofcurvature.

Although in the embodiment illustrated in FIG. 1 the first center pointC₁ of the first reflow key 100 and the second center point C₂ of thesecond reflow key 200 are shown as positioned at the same site, thefirst center point C, and the second center point C₂ may be positionedat different sites. In particular, a position of the first center pointC₁ of the first reflow key 100 and a position of the second center pointC₂ of the second reflow key 200 may be moved according to a reflowtendency of the first and second reflow keys 100 and 200 after therespective reflow processes, which will be described later.

The first reflow key 100 and the second reflow key 200 are formed of aphotoresist material. Positive photoresist or negative photoresist maybe selectively used as the photoresist material of the first and secondreflow keys 100 and 200. The first reflow key 100 and the second reflowkey 200 may be formed in a test element group (TEG) region where a testdevice for measuring an electrical property of the actual device formedon a device region of the semiconductor substrate is formed. Also, thefirst reflow key 100 and the second reflow key 200 may be formed of thesame material as a resist pattern formed as a mask pattern for forming adesired pattern on the device region.

In the exemplary embodiment shown in FIG. 1, the plurality of firstpattern elements 110, 120, 130 and 140 is four first pattern elements110, 120, 130 and 140, each constituting a side of the first reflow key100, which is shown having a rectangular shape. Similarly, the pluralityof second pattern elements 210, 220, 230 and 240 is four second patternelements 210, 220, 230 and 240, each constituting a side of the secondreflow key 200, which also has a rectangular shape. Although FIG. 1illustrates the first reflow key 100 and the second reflow key 200having a rectangular shape, the first reflow key 100 and the secondreflow key 200 are not limited to that shape and may be have variousother shapes.

By way of further alternative, although FIG. 1 illustrates the secondreflow key 200 having a size smaller than the first reflow key 100 andbeing formed within a region defined by the first reflow key 100, thepresent invention is not limited to this particular arrangement.

The first pattern elements 110, 120, 130, and 140 of the first reflowkey 100 may be arranged such that the portion having a larger radius ofcurvature, i.e., the second pattern shape portion 104, is disposed on aside facing a first predetermined direction, e.g., a direction indicatedby an arrow “A”, of a line extending diagonally through the first centerpoint C₁. In addition, the second pattern elements 210, 220, 230, and240 of the second reflow key 200 may be arranged such that the portionhaving a larger radius of curvature, i.e., the fourth pattern shapeportion 204, is disposed on a side facing a second predetermineddirection, which is opposite to the first direction, e.g., a directionindicated by an arrow “B,” which is opposite to the arrow “A” direction,of a line extending diagonally through the second center point C₂.

In the exemplary construction of the first and second reflow keys 100and 200 shown in FIG. 1, the first and second reflow keys 100 and 200are arranged such that two of the plurality of first pattern shapeportions 102 of the first pattern elements 110 and 120 face acorresponding two of the plurality of third pattern shape portions 202of the second pattern elements 210 and 220. Concurrently, the firstreflow key 100 and the second reflow key 200 are arranged such that twoof the plurality of second pattern shape portions 104 of the firstpattern elements 130 and 140 face a corresponding two of the pluralityof fourth pattern shape portions 204 of the second pattern elements 230and 240.

In the above-described arrangement for the second pattern shape portion104 of the first pattern elements 110, 120, 130, 140 to exist at theside facing the arrow “A” direction and for the fourth pattern shapeportion 204 in the second pattern elements 210, 220, 230, 240 to facethe direction indicated by the arrow “B”, the first reflow key 100 andthe second reflow key 200 may be arranged such that an area where thefirst pattern shape portion 102 of the first pattern elements 110 and120 faces the third pattern shape portion 202 of the second patternelements 210 and 220 and an area where the second pattern shape portion104 of the first pattern elements 130 and 140 faces the fourth patternshape portion 204 of the second pattern elements 230 and 240 coexist.

As shown in FIG. 1, in the arrangement that the second pattern shapeportion 104 having the relatively larger radius of curvature in thefirst pattern elements 110, 120, 130, 140 faces in the “A” direction andthe fourth pattern shape portion 204 having the relatively larger radiusof curvature in the second pattern elements 210, 220, 230, 240 faces inthe “B” direction, after the reflow process for the photoresist patternformed on the device region is performed, the resist reflow measurementkey 50 including the first reflow key 100 and the second reflow key 200is also reflowed concurrently with the reflow of the resist pattern. Atthis time, the resist of the first pattern shape portion 102 and thethird pattern shape portion 202, which have the relatively smallerradius of curvature, flows more than the resist of the second patternshape portion 104 and the fourth pattern shape portion 204, which havethe relatively larger radius of curvature.

A relationship between the radius of curvature of the resist pattern andan amount of flow will now be described in detail.

Generally, when a photoresist material flows, flow behavior of thephotoresist material is influenced by the pattern shape. Especially, asthe curvature radius is reduced, more much photoresist material flows.

FIG. 2 shows a series of SEM photographs observed through afterdevelopment inspection (ADI) before a photoresist material flows and SEMphotographs observed through after flow inspection (AFI) after thephotoresist material flows.

As shown in FIG. 2, in a case of the line and space (US) patterns,pattern asymmetry is observed at a dummy line located at the outermostportion (i.e., the rightmost line) in the case of AFI in contrast to thecase of ADI. When comparing ADI with AFI in an island contact typepattern, more much flow is generated at an upper portion and a lowerportion having a smaller radius of curvature in the respective patterns.Thus, as shown in FIG. 2, it is known that a reduction in a length in alongitudinal vertical axis direction of each pattern is larger than areduction amount in CD of each pattern in the horizontal direction. Fromthe above result, it is known that a portion having a smaller radius ofcurvature flows more than a portion having a larger radius of curvaturewhen the resist pattern flows.

As described above, since the first pattern shape portion 102 and thethird pattern shape portion 202 having a relatively smaller radius ofcurvature flow more than the second pattern shape portion 104 and thefourth pattern shape portion 204, each first center line 100 c of theplurality of first pattern elements 110, 120, 130 and 140 is shiftedtoward the second pattern shape portion 104 having the relatively largerradius of curvature. Similarly, the second center line 200 c of theplurality of second pattern elements 210, 220, 230 and 240 of the secondreflow key 200 is shifted toward the fourth pattern shape portion 204having the relatively larger radius of curvature. As a result, the firstcenter point C₁ of the first reflow key 100 moves toward in the “A”direction and the second center point C₂ of the second reflow key 200moves in the “B” direction. Thus, it is possible to control the flow ofthe resist pattern arranged on the device region of the semiconductorsubstrate based on the amount of variation in the position of the firstcenter point C₁ of the first reflow key 100 and the amount of variationin the position of the second center point C₂ of the second reflow key200. If necessary, a relationship between the amounts of variation inthe positions of the first and second center points C, and C₂ and theflow of the resist pattern can be quantified through a simulation.

The first pattern shape portion 102 of the first pattern elements 110,120, 130 and 140 and the third pattern shape portion 202 of the secondpattern elements 210, 220, 230 and 240 may be formed to have the sameradius of curvature. In addition, the second pattern shape portion 104of the first pattern elements 110, 120, 130 and 140 and the fourthpattern shape portion 204 of the second pattern elements 210, 220, 230and 240 may be formed to have the same radius of curvature.

FIG. 3 illustrates a sectional view of the resist reflow measurement key50 taken along line II-II′ of FIG. 1 and shows the first reflow key 100and the second reflow key 200 being designed in a trench type patternformed in a resist layer 20 on a semiconductor substrate 10.

FIG. 4 illustrates a sectional view of an alternate resist reflowmeasurement key 50′ taken along line II-II′ of FIG. 1 and shows thefirst reflow key 100′ and the second reflow key 200′ being designed in amesa type pattern on a semiconductor substrate 10.

As shown in FIGS. 3 and 4, in a resist reflow measurement key accordingto an embodiment of the present invention, the first reflow key 100 andthe second reflow key 200 may be designed in a trench type pattern or amesa type pattern.

FIG. 5 is a flow chart of a method of forming a fine pattern of asemiconductor device according to an embodiment of the presentinvention.

Referring to FIG. 5, in step 310, a resist pattern is first formed on asemiconductor substrate to form a pattern having a predetermined shape.The resist pattern can be made in any desired pattern, e.g., in acontact hole pattern or in a line and space pattern. Additionally, aresist reflow measurement key 50 according to an embodiment of thepresent invention as described in connection with FIGS. 1, 3 and 4 isconcurrently formed on the semiconductor substrate during the formationof the resist pattern. As described previously, the resist pattern andthe resist reflow measurement key 50 may be formed of an identicalmaterial. The resist pattern may be formed on a device region of thesemiconductor substrate where an actual device is formed. The resistreflow measurement key 50 may be formed at a test element group (TEG)region where a test device for measuring an electrical property of theactual device is formed.

In step 320, the resist pattern and the resist reflow measurement key 50are reflowed at the same time. At this time, so as to reflow the resistpattern and the resist reflow measurement key 50, the same reactioncondition is applied. The reflowing of the resist pattern and the resistreflow measurement key 50 is not limited only to a method using heat,but any reflow method known to those skilled to the art is applicable.

In step 330, a variation in position of the first center point C₁ and avariation in position of the second center point C₂ of the reflowedresist reflow measurement key 50 are measured by using an opticaloverlay measurement apparatus, which is generally used for measuringoverlay in a semiconductor device fabrication process. This measurementis performed in the general AFI step. Any optical overlay measurementapparatus that is well known to those skilled in the art can be used.For example, in a laser scan alignment (LSA) type overlay measurementapparatus, the resist reflow measurement key 50 is scanned using a shortwavelength of laser or a broad band wavelength to read out the centerpoint value of the resist reflow measurement key 50. Alternatively, in afield image alignment (FIA) type overlay measurement apparatus, theshape of the resist reflow measurement key 50 is inputted into a chargedcoupled display (CCD) like a camera measurement, is read out by signalprocessing, and a shadow thereof is discriminated to read out the centerpoint value of the resist reflow measurement key 50.

In step 340, a critical dimension (CD) of the reflowed resist pattern isdetermined from measurement values of the variation in the position ofthe first center point C₁ and the variation in the position of thesecond center point C₂.

The reflow process is controlled such that the flow of the resistpattern is monitored on the basis of the CD value indirectly determinedthrough the resist reflow measurement key 50 in the AFI step accordingto the aforementioned sequence. This control allows a finally desired CDvalue of the resist pattern to be obtained.

The resist reflow measurement key according to an embodiment of thepresent invention includes a first reflow key and a second reflow keyeach including a plurality of pattern elements having different radii ofcurvature. The resist reflow measurement key according to an embodimentof the present invention is formed on the same plane as the resistpattern formed on the device region of a semiconductor substrate, andmay be formed of an identical material to the resist pattern.Accordingly, after the reflow process of the resist pattern formed onthe device region of the wafer is performed, a variation in thepositions of the center points on the basis of the flow amount of theresist reflow measurement key reflowed concurrently with the resistpattern is measured in the AFI step using a general overlay measurementapparatus to thereby monitor the CD of the resist pattern.

According to the present invention, it is possible to quantify the flowof the resist pattern placed on the device region by measuring only theresist reflow measurement key in an AFI step. Accordingly, the flow ofthe resist pattern on the wafer in AFI step can be monitored within avery short time, thereby increasing throughput when performing a processon a large-sized wafer. Also, in the reflow process of the resistpattern, feedback can be rapidly performed, AFI monitoring turn aroundtime (TAT) can be shortened, and the pattern uniformity according to theposition on the wafer can be enhanced.

Exemplary embodiments of the present invention have been disclosedherein and, although specific terms are employed, they are used and areto be interpreted in a generic and descriptive sense only and not forpurpose of limitation. Accordingly, it will be understood by those ofordinary skill in the art that various changes in form and details maybe made without departing from the spirit and scope of the presentinvention as set forth in the following claims.

1. A resist reflow measurement key, comprising: a first reflow keydisposed on a substrate around a first center point, the first reflowkey including a plurality of first pattern elements each having a firstpattern with a first radius of curvature located on a first side of afirst center line extending in a lengthwise direction of each of theplurality of first pattern elements and a second pattern with a secondradius of curvature located on a second side of the first center line,which is opposite to the first side of the first center line; and asecond reflow key disposed on the substrate around a second centerpoint, the second reflow key including a plurality of second patternelements each having a third pattern with a third radius of curvaturelocated on a first side of a second center line extending in alengthwise direction of each of the plurality of second pattern elementsand a fourth pattern with a fourth radius of curvature located on asecond side of the second center line, which is opposite to the firstside of the second center line, the second reflow key being formed on asame plane as the first reflow key.
 2. The resist reflow measurement keyas claimed in claim 1, wherein the first reflow key has a rectangularshape and the plurality of first pattern elements is four first patternelements, each one of the four first pattern elements constituting aside of the rectangular shaped first reflow key.
 3. The resist reflowmeasurement key as claimed in claim 1, wherein the second reflow key hasa rectangular shape and the plurality of second pattern elements is foursecond pattern elements, each one of the four second pattern elementsconstituting a side of the rectangular shaped second reflow key.
 4. Theresist reflow measurement key as claimed in claim 1, wherein the firstpattern of each of the plurality of first pattern elements is aplurality of first pattern shape portions positioned at the first sideof the first center line and having the first radius of curvature, andthe second pattern of each of the plurality of first pattern elements isa plurality of second pattern shape portions positioned at the secondside of the first center line and having the second radius of curvature,which is larger than the first radius of curvature, and the thirdpattern of the plurality of second pattern elements is a plurality ofthird pattern shape portions positioned at the first side of the secondcenter line and having the third radius of curvature, and the fourthpattern of the plurality of second pattern elements is a plurality offourth pattern shape portions positioned at the second side of thesecond center line and having the fourth radius of curvature, which islarger than the third radius of curvature.
 5. The resist reflowmeasurement key as claimed in claim 4, wherein the plurality of firstpattern elements are respectively arranged such that the plurality ofsecond pattern shape portions is disposed facing a first direction of aline extending diagonally through the first center point, and theplurality of second pattern elements are respectively arranged such thatthe plurality of fourth pattern shape portions is disposed facing asecond direction, which is opposite to the first direction, of a lineextending diagonally through the second center point.
 6. The resistreflow measurement key as claimed in claim 4, wherein the first andsecond reflow keys are respectively arranged such that at least one ofthe plurality of first pattern shape portions of the plurality of firstpattern elements faces a corresponding one of the plurality of thirdpattern shape portions of the plurality of second pattern elements. 7.The resist reflow measurement key as claimed in claim 4, wherein thefirst reflow key and the second reflow key are respectively arrangedsuch that at least one of the plurality of second pattern shape portionsof the plurality of first pattern elements faces a corresponding one ofthe plurality of fourth pattern shape portions of the plurality ofsecond pattern elements.
 8. The resist reflow measurement key as claimedin claim 6, wherein the first reflow key and the second reflow key arerespectively arranged such that at least one of the plurality of firstpattern shape portions of the plurality of first pattern elements facesa corresponding one of the plurality of third pattern shape portions ofthe plurality of second pattern elements and at least one of theplurality of second pattern shape portions of the plurality of firstpattern elements faces a corresponding one of the plurality of fourthpattern shape portions of the plurality of second pattern elementsconcurrently.
 9. The resist reflow measurement key as claimed in claim4, wherein the first radius of curvature and the third radius ofcurvature are the same.
 10. The resist reflow measurement key as claimedin claim 4, wherein the second radius of curvature and the fourth radiusof curvature are the same.
 11. The resist reflow measurement key asclaimed in claim 1, wherein the second reflow key has a size smallerthan a size of the first reflow key.
 12. The resist reflow measurementkey as claimed in claim 11, wherein the second reflow key is formed in aregion defined by the first reflow key.
 13. The resist reflowmeasurement key as claimed in claim 1, wherein the first and secondreflow keys are each of a trench type pattern.
 14. The resist reflowmeasurement key as claimed in claim 1, wherein the first and secondreflow keys are each of a mesa type pattern.
 15. The resist reflowmeasurement key as claimed in claim 1, wherein the first reflow key andthe second reflow key are formed of a material selected from positivephotoresist and negative photoresist.
 16. A method of forming a finepattern of a semiconductor device, the method comprising: forming aresist pattern on a semiconductor substrate to form a pattern having apredetermined shape; forming a resist reflow measurement key on thesemiconductor substrate while forming the resist pattern; reflowing theresist pattern and the resist reflow measurement key at the same time;measuring a variation in a position of a first center point of thereflowed resist reflow measurement key and a variation in a position ofa second center point of the reflowed resist reflow measurement key byusing an optical overlay measurement apparatus; and determining acritical dimension of the reflowed resist pattern from measurementvalues of the variation in the position of the first center point andthe variation in the position of the second center point.
 17. The methodas claimed in claim 16, wherein the pattern having the predeterminedshape is a contact hole pattern or a line and space pattern.
 18. Themethod as claimed in claim 16, wherein the optical overlay measurementapparatus is a laser scan alignment (LSA) type overlay measurementapparatus or a field image alignment (FIA) type overlay measurementapparatus.
 19. The method as claimed in claim 16, wherein the resistpattern and the resist reflow measurement key are formed of an identicalmaterial.
 20. The method as claimed in claim 16, wherein thesemiconductor substrate comprises a device region where an actual deviceis formed, and a test element group (TEG) region where a test device formeasuring an electrical property of the actual device is formed, theresist pattern being formed in the device region, and the resist reflowmeasurement key being formed in the TEG region.